The shoulder joint is a ball-and-socket joint which has an exceptional range of motion. Shoulder instability and other maladies of the shoulder joint, such as arthrosis or fracture, may require a replacement of the joint.
A shoulder joint prosthesis which includes the replacement of the convex head of the humerus is disclosed in U.S. Pat. No. 7,819,923. It reflects the orientation and the center of rotation of actual joints. In the case of a worn or damaged rotator cuff or too much bone loss, such a prosthesis would not recover the range of motion. In such case, a reverse shoulder prosthesis may be preferable. An example of such a prosthesis is disclosed in U.S. Patent Application Publication No. 2009/0210065, where the prosthesis includes a humeral component with a stem and a cup attached to the stem. The glenoid component supports a convex head which articulates with the cup of the humeral component.
To obtain a maximum range of motion, the prosthesis must be adapted to the individual case. Specifically, the position of the cup of the humeral component with respect to the stem is critical. The cup disclosed in U.S. Patent Application Publication No. 2009/0210065 may be pivoted about the axis of the stem.
Instability and other maladies of human joints, such as arthrosis or fracture, can be sufficiently acute that prosthetic replacement of compromised joint features may be indicated. For example, in shoulder reconstruction, the humeral head may be replaced by first resecting the humeral head from the humerus and then installing a humeral prosthetic at the resection.